On the Road Again - volume 4 - Page 15

Ummm, the "last post" in threads isn't showing up for a LONG while. Example, my previous post (made at 06:20) still isn't visible. FWIW.

Anyways, does anyone remember if Oppy has done any APX on the fracture fills we've come across-- I seem to think of something at Erebus/Olympia, but can't find anything. The current targets, with the extensive fracture fills, will be ideal for MI and APX work. Once we get a better handle on composition and structure, we'll have a better understanding the conditions at the time.

--Bill

On sol 1462 an APXS measurment was done on this fracture fill.

Here are all the images of that area.

And here are the sol 2145 images.

Ah, that's right-- the MER Analyst's Notebook. That had slipped my mind.

Rock hedge at Gilbert. Rock hedge, Rock Ridge, Rock Ridge...

--Bill

Wow, This has got to be one of the more intriguing MI targets in a long time:

Horton, Thanks for the 3D pairs of this rock (center-left) that seems to carry a lot of fracture fill that may also be coated is places with a thin layer of tiny spherules. This could be an "aha" moment. The detached fracture fill that was studied at Duck Bay had lots of hematite.

You should be wary of the color in the 2145 images, as I "patched" areas with missing data with synthesized values - especially in the lower portion of the image in reply 284.

I will redo these images when the data is available.

But in the meantime, have a look ar some of the really interesting blueberry stems on the "Chocolate Hills" targets:

I have contended from day one that the blueberry stems are intrinsic to the blueberries - not the rock matrix.

SO; how in a very short time ( geologically speaking ) does the wind sculpt blueberry stems in the rock matrix in wind protected areas - like cracks? HmmMMM??

Horton, thanks for those superb 3D images.

I'm thinking one way of reconciling a young age for the crater with seemingly extensive erosion is to suppose that the ejecta initially contains some extremely hyper-erosive material that we never see with the older craters because it is completely gone.

I am also thinking that in some cases the blueberries + stems look more like the original matrix and the sulphate material looks more like a subsequent deposit---the opposite of the conventional assumption.

I am also reminded of the Pot-of-Gold rock in the Spirit trek that had prominent berries on stems before we noticed them on Oppy rocks.

Hort; Re. #285, the wind can do anything on Mars. But perhaps it might not be wind that is doing the sculpting but miniscule trickles of water or water vapour moving through the cracks on a regular basis for many years.

Winston

Kye;

I agree. Look at this

Winston

When I get data dropouts, I just "patch" the area with an appropriate gray fill, which let the two other channels get by well enough, and wait for a revised image.

New Rover update at the MER/JPL site.

[link] #sol2137

wherein they speculate that "some of the rocks exhibit a dark crust, potentially impact melt". sheesh. Not likely with a low-energy 40m crater. Who writes these blurbs for them?

--Bill

Kye re. your #284

See this

Winston

Horton, re your 285, I'm always happy to read of scepticism regarding the saltating sand scour explanation of the berry stems. We've been looking at the stems for so long it is easy to forget that the scour model requires that a depth of material of the same order as the length of the stems has to be removed from the entire surface of the rock while the fragile stems survive. The wind direction would have to be extremely regular and the stems would all have to point directly into the local wind. Having stems close together but pointing in different directions is a fatal problem for the sand scour theory. Yes, air currents can be affected by the local surface to move in directions other than the prevailing wind direction, but saltating sand grains cannot follow these currents at a small scale. Saltating sand should be moving at about a third to a half the wind speed which is comparable to Earth. These particles have plenty of inertia - just as much as on Earth - and there's only one hundredth the air to push them off a basically ballistic flight path. No, saltating sand grains just can't go around tight corners with the air flow. Suspended particles can, and this is close to being the definition of the difference between the two modes of transport. Scour by suspended particles is possible but would take much longer to accomplish significant erosion.

And Horton again, Thanks again, for the 3D pair of that rock with the extensive fill. (See my 284) If anyone hasn't looked at Horton's binocular and colored version please do. Without the 3D it is hopeless. I think that this is a fracture fill that was present before the Conception impact and is now revealed face-on because the impact broke the rock along the filled fracture. There are two different layers of material. A rough textured layer toward the viewer is less complete than the smoother layer under it, but the rough layer seems to be of uniform thickness as if cast in the fracture with the smooth layer. Both are bluish compared with the other material of the rock. These two layers remind me of the laminated fill Roosevelt, or perhaps this could have something to do with why the fills usually don't fill the fractures.

Bill; If these vertical open fractures are just enlarged dessication cracks, the rock would have to be somewhat indurated .
Don't you think subsequent erosion would therefore require a bit of time, particularly in Mars current atmosphere?

BTW on another forum it would be near blasphemy to cast disparaging remarks about the writers at the MER/JPL.

Barsoomer, re. your #284
You said in response to Hort’s query about an apparent anomaly re. berries on stems being produced in the cracks of oppy’s rocks that were imaged today; “I am also thinking that in some cases the blueberries + stems look more like the original matrix and the sulphate material looks more like a subsequent deposit---the opposite of the conventional assumption.”
I have held that hypothetical position from very early in the Oppy adventure. My view then and now being that ;
1) The berries are a surface phenomenon and are being produced now at the surface and this process has been going on for untold eons
2) The berries are initially produced in the “plains” areas, and are covered in pavement evaporite in the inter crater areas. Thus the purgatory images that showed “emerging berries” after only a few weeks of exposure to the atmosphere is typical of all of meridiani which we have seen.
3) These buried berries, with their attached stems eventually, become bedrock as the millennia go by and more dust and berries cover them.
4) The ejecta stones are merely blocks of consolidated mixtures of berries, dust and evaporate bonding material that are blasted to the surface by the impact.
5) Depending on how far below the surface they come from the berries may be relatively loosely held and erosion by wind or by water/vapour action can quickly expose them to the atmosphere (weeks instead of millennia)
6) Berries can also form on the surfaces of evaporate rocks in cracks and in the bluish matrix seen in microchannels
7) Some unique characteristic of Meridiani’s subsoil / subsurface environment is responsible for the berries. E.g. throughout meridian as explored by Oppy, numerous sink holes, depressions, minicraters, holes that look like water has just flowed through them onto the surface, there are indications that the surface is being sculpted at a micro level in the present. I think the berries are not just haematite and there are numerous images which suggest that this might be true.
Kye; re. today’s pancams, and especially the one you referred to in your #284, I am quite excited to see if they will do some MI’s of what you call “fracture fill” on the rock. i.e. the area that shows up as a distinct bluish greenish area on the surface of the large rock in the mid-left area of the image. That area may indeed be fracture fill but I think it could also be something else. Shouldn’t fracture fill be associated with a fracture? Where is the fracture in this case? The different shades of blue-green in the area are very provocative. I’m hoping they do some MI’s soon without disturbing the surface and then with relatively light ratting to get some idea of the structure of the “fracture fill”.
The berry images seen over the last week or so have inspired me to look back at a number of Oppy images throughout its quest and I realize that I had forgotten the huge number of images that suggest that there could be some reasonable challenges to the official version of the development of berries and even the influence of water at or near the surface.

Winston

There is induration and then there is induration. If this were cemented with silica with heat and pressure, it would be very hard. This is basically a fine, dirty sand cemented with Kieserite (Epsom Salts), with a Mohs hardness of, what, 3.5?

And, as I noted earlier in Post 280, this weathering material is quite friable (crumbly).

This will prove to be a good stop to observe weathering processes. Great discussions thus far!

Blasphemy? They should know better! They are, after all, rocket scientists.

--Bill

New Navcams and Pancams up this AM. Nothing earthshaking on first look, but more picturesque.

Here is a good online intro to cratering processes. Out of print and somwhat dated, but still sound. A bigga boom is still a bigga boom.

[link]

And a couple of references to dunes and aeolian processes:

http://www.nps.gov/archive/whsa/Sand%20Dune%20Geology.htm

--Bill

http://pubs.usgs.gov/gip/deserts/dunes/

In the new "horizon view" with today's Pancam, I noticed a new horizon feature-- looks to be nearer than "just over the horizon". Anyone got a Google Mars/HiRISE image that goes that far south?

5X vertical exaggeration:

--Bill

Bill Harris, Thanks for that crater formation reference link in your 295. It is the most complete that I have come across. I'm not really expecting an answer to the following mystery which seems to be part of every reference article that I've read so far: The diagrams always show uplifted bedrock strata around the crater but the text never explains how this happens. For example see Chapter 3 page 21 of that link in 295. The diagrams of simple crater formation show a raised bedrock rim at the end of the event similar in height (depth) to the rim ejecta deposits. How is this possible? What is supporting the bedrock that has been lifted to a higher elevation during the event? Where does the extra volume of material come from and how does it get underneath the lifted bedrock? Does the uplifted area have to be extensively fractured and the fractures then account for the extra volume? These particular drawings show "bent" bedrock strata out to a third of the crater diameter beyond the rim but they do not even indicate that it is all fractured. I'll be sceptical that bedrock is raised around impact craters at all until I find an explanation. If any cratering experts are lurking please contribute.

LWS, re your 293, I think that this particular fracture fill has been excavated by the impact. It was present as a filled fracture in the bedrock before the event and the impact brecciation followed the already-present weakness of the filled fracture. We've seen at least one fracture fill in breccia at Concepcion with both sides of the fracture still attached. There are what look like fills in the ejecta of Beagle Crater which I thought might be an indication that the fills formed after the Beagle impact, but now I am inclined to accept that they where probably present in bedrock fractures before the impact and have stayed attached to a breccia block that just happened to end up on the surface where we can see it (lower right):

Re blueberries.
The recent images suggest at least two distinct populations of 'blueberries.' One is confined to, and, upon erosive action, emerges from exposed strata. These layer-bound berries indicate formation within soil horizons after deposition, rather than emplacement as lapilli or by other 'air-fall' theory.
The second population appears to be randomly distributed upon the eroded surfaces of boulders, etc. This suggests more recent and perhaps on-going formation in place; or transportation by some broadcasting mechanism - volcanism, high winds, ice, floods.
As for the stems... Besides the wind-shadowing effect of the berries, the stems themselves could be somewhat more resistant than the surrounding rock. This would be particularly true if the berry-bearing sediments formed underwater. Even gentle currents (not berries) could cause 'tails' to form downstream or with surprising convolutions and slightly compact the affected materials. End result could be preserved and subsequently exhumed and eroded for our perusal.

sol 2145 map position looking southwards:

Bill, the feature on the horizon in reply 296 seems to be the south rim of the larger ( 17 meter ) crater of the double crater in the lower left corner.

In the sol 2140 panorama the feature is 0.4 degrees wide - which translates into about 5 meters at the 670 meters distance to the crater.

There appears to be a raised south rim of the 17 meter crater about 5 meters long.

Agreed, Hort. There is the high area of the rim of one of the pair of craters, and about 2/3 of the way to the "twins", to the East, is a light-colored (reddish) bedrock area, and closer in you can see the shadows (especially in L7) of three closer tall ripples. We'll get closer looks as we go by it (now, _those_ do look like 1000 year old craters).

Answered my owm question, actually. I finally broke down and got the newest Java version, so I can use the IAS viewer at the HiRISE site.

--Bill